The present invention relates to a method and apparatus for controlling a circular accelerator for accelerating a charged particle beam injected thereto to emit the accelerated beam and more particularly to a control method and apparatus of a circular accelerator for performing injection, acceleration and emission of a charged particle beam on the basis of a clock pulse.
As a control method of a circular accelerator for accelerating a charged particle beam injected thereto to emit the accelerated beam, there is a method of controlling injection, acceleration, emission and deceleration of a charged particle beam in a circular accelerator on the basis of a clock pulse generated from a pulse generator at a fixed period.
More particularly, when injection, acceleration, emission and deceleration of the charged particle beam is performed in the circular accelerator, a pattern of command values (for example, current values) to be supplied to devices such as an electromagnet and a high-frequency accelerating cavity constituting the circular accelerator is previously stored in corresponding manner to the number of clock pulses and the previously stored command values are supplied to the devices on the basis of the number of clock pulses generated from the pulse generator. The stored command values are repeatedly supplied to the devices of the circular accelerator, so that the circular accelerator performs injection, acceleration, emission and deceleration at a fixed period repeatedly.
The charged particle beam emitted from the circular accelerator is used in various fields such as medical treatment for a cancer patient and sterilization of food, while it is desired that the charged particle beam is emitted in accordance with a state of an object to be irradiated in any cases. Particularly, when the charged particle beam is used for treatment of cancer, a position of the diseased part is changed in accordance with breath, heartbeat or the like of a patient and accordingly the diseased part cannot be irradiated with the charged particle beam if the circular accelerator is not controlled to emit the charged particle beam when the diseased part is located in a set position. That is, it is desired that the timing of emission of the charged particle beam in the circular accelerator can be adjusted in accordance with a changed position of the diseased part.
In the prior art, however, previously set command values are supplied to the devices in accordance with the clock pulse generated at a fixed period and accordingly injection, acceleration, emission and deceleration of the charged particle beam are performed at a fixed period, so that the timing of emission in the circular acceleration cannot be adjusted.
It is an object of the present invention to provide a control method and apparatus of a circular accelerator capable of adjusting the timing of emission of a charged particle beam.
In order to achieve the above object, according to the present invention, in a control method of a circular accelerator for controlling timing of injection, acceleration and emission of a charged particle beam in the circular accelerator on the basis of a clock pulse generated at a set period, generation of the clock pulse is suspended after acceleration of the charged particle beam has been ended and generation of the clock pulse is resumed when a beam irradiation request is produced on the basis of a state of an object to be irradiated during the suspension state of generation of the clock pulse.
Since the generation of the clock pulse is suspended after the acceleration of the charged particle beam has been ended and the generation of the clock pulse is resumed when the beam irradiation request is produced during the suspension state of generation of the clock pulse, the resumption timing of generation of the clock pulse can be adjusted in accordance with the timing that the beam irradiation request is produced and accordingly the timing of emission of the charged particle beam can be controlled on the basis of the clock pulse.